code: def test_heatmap_to_image_grayscale(heatmap, boxl):
      gray_heatmap = heatmap_to_image(heatmap)
      assert heatmap.shape == (gray_heatmap.width, gray_heatmap.height)
      assert_pixel_by_pixel_equal(gray_heatmap, boxl)
  
imports: import pytest
  import numpy
  from eli5.base import Explanation, TargetExplanation
  from eli5.formatters.image import format_as_image, heatmap_to_image, expand_heatmap, _validate_heatmap, _update_alpha, _cap_alpha, _overlay_heatmap
  from .utils_image import assert_pixel_by_pixel_equal
label_desc: Use image node_id 7 for calling a global function with example usage: test_heatmap_to_image_grayscale(heatmap, boxl) without return types